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PubMed1991

Congenital hyperammonemia: symptomatic carrier girl patient and her asymptomatic heterozygous mother for ornithine transcarbamylase (OTC) deficiency: specific enzyme diagnostic and kinetic investigations for the detection of heterozygous genostatus.

Activities of the specific enzymes of the inherited hyperammonemic syndromes (carbamoyl-phosphate synthetase CPS), ornithine transcarbamylase (OTC), arginine-succinate-synthetase (ASS), arginine-succinate-lyase (ASL) and arginase (ASE) were measured in a liver biopsy specimen of a 2 years-old girl suffering from chronic hyperammonemia and in the erythrocyte- and leukocyte-homogenisate of her parents. The activity of OTC in liver homogenisate of the patient was 62.9 percent; in the leukocytes of the parents it was 78.5 percent (in mother) and 102 per cent (in the father) as compared to the controls. Our patient proved to be a symptomatic carrier of OTC deficiency and her mother proved to be an asymptomatic carrier.

Ammonia↗
PubMed1991

Activities of purine catabolism related enzymes in zinc deficiency: relationship to T-lymphocyte dysfunction and hyperammonemia.

The activities of liver, muscle, and red blood cell enzymes involved in the degradation of purine were assayed in zinc deficient (ZD), pair-fed control (PF) and ad libitum-fed control (Ad lib) rats. Diets (1.5 ppm of zinc in ZD diet and 110 ppm in control diet) were fed to rats for 6 weeks after which they were sacrificed and tissues isolated for several assays. Results indicated a significant increase in the concentration of plasma NH3 (P less than .0005) and uric acid (P less than .05), and a decrease in the concentration of blood urea nitrogen (BUN) (P less than .025) in ZD rats compared to both control groups. The activities of liver and red blood cell (RBC) nucleoside phosphorylase (NPase) were lower (P less than .025) in ZD rats. Activity of 5'adenosine monophosphate deaminase (AMPDA) was higher in liver (P less than .0001) and muscle (P less than .01) in ZD groups vs. controls. Activity of hypoxanthine polyribosyl transferase (HPRT) in liver was higher (P less than .005) in ZD group compared to controls. The present findings could be viewed from two aspects: first, they provide an insight into the specific role of zinc on T-lymphocyte function which is believed to be mediated by the regulatory effect of zinc on the enzyme nucleoside phosphorylase and, second they provide a possible mechanism for hyperammonemia observed in zinc deficient human subjects and experimental animals.

Adenosine Deaminase↗
PubMed1986

Trimethyltin-induced alterations in brain amino acids, amines and amine metabolites: relationship to hyperammonemia.

An investigation of several neurochemical consequences of exposure of the rat to 3/4 of the estimated single injection LD50 quantity of trimethyltin chloride (TMT) indicated that a significant elevation in the levels of glutamine (Gln) and 5-hydroxyindole acetic acid (5-HIAA) occurred at post-dosing day 7 in each examined region of the brain; elevated Gln persisted in the hippocampus through day 14 and returned to control levels at day 28. At post-dosing day 7, levels of glutamate were decreased in the hippocampus, while levels of GABA were decreased in hippocampus and frontal cortex, but not in corpus striatum; hippocampal glutamate and GABA returned to control levels by post-dosing day 14. Decreased levels of taurine (Tau) occurred on day 7 in both hippocampus and frontal cortex; hippocampal Tau remained below control levels through post-dosing day 28. Levels of other amino acids and of amines and amine metabolites were not altered by TMT in the 7 to 28 day post-dosing interval. At day 7, TMT treatment did not alter brain regional activities of glutamine synthetase; however, plasma ammonia was elevated 100% above the control value. Alterations in several serum enzymes (esp., alkaline phosphatase and aspartate aminotransferase) revealed several other peripheral consequences of TMT exposure which persist through post-dosing day 28. The more prominent and wide-spread neurochemical alterations resulting from TMT exposure appear to reflect consequences of hyperammonemia resulting from a peripheral effect of the organotin compound.

Amino Acids↗
PubMedDate not supplied

Enzymatic screening of genetic diseases. (Including hyperammonemia).

The application of the techniques of clinical enzymology to the study of human biochemical genetics has laid the foundations for the practice of clinical genetics. In the study of inborn errors of metabolism of the urea cycle, these investigations have resulted in an understanding of the pathophysiology of hyperammonemia as well as delineating additional information on the molecular mechanisms of ammonia detosification. Insight has been obtained through recent investigations of another group of genetic disorders, hypercholesterolemia, which has resulted in opening new horizons relating to metabolic regulation of enzyme action through effector-receptor interactions at cell surfaces.

Ammonia↗
PubMedDate not supplied

Sclerema neonatorum: a sign of transient hyperammonemia of the newborn.

We cared for four neonates with transient hyperammonemia of the newborn (THAN), all of whom exhibited sclerema during their course. Sclerema is a hardening of the subcutaneous tissues, which gives the tissue a firm, rubber-like quality. This association has not been previously reported, and it may provide a clue to early diagnosis and intervention in THAN.

Ammonia↗
PubMed1987

[Transient symptomatic neonatal hyperammonemia].

Premature newborns suffering from respiratory distress and asphyxiated term newborns may present transient symptomatic neonatal hyperammonemia associated with reversible neonatal coma. As they survive they may develop normally; however the authors emphasize the importance of concomitant hemodynamic disorders and the extreme frequency of brain hemorrhage and ischemia. Ultrasonography or tomodensitometry are necessary for prognosis.

Ammonia↗
PubMed1977

[Hyperammonemia and hepatic encephalopathy in cirrhotics receiving spironolactone (author's transl)].

The aim of this study was to specify the mechanism of hepatic encephalopathy which may occur in some cirrhotics treated by Spironolactone. In 31 cirrhotics with ascite, this diuretic induced a significant increase in arterial ammonemia; 8 patients developed an impending hepatic coma which was associated with ammonemia levels significantly higher than those observed in the patients without encephalopathy at the end of the treatment. Hyperammonemia induced by Spironolactone does not result from a muscular, renal or hepatic ammonia production but seems related to an increased intestinal ammoniagenesis which which is secondary to the bacterial hydrolysis of urea in the colon; indeed, there is a significant correlation between the ammonemia increase and the simultaneous rise in blood urea during treatment.

Adult↗
PubMed1981

[Lysinuric protein intolerance: a severe hyperammonemia secondary to l-arginine deficiency (author's transl)]].

Lysinuric protein intolerance is an autosomal recessive disease, due to a defect in intestinal, renal and hepatic dibasic amino acid transport. Two new cases in the same family are reported. The disease appears progressively during the first months of life with failure to thrive, anorexia, vomiting, diarrhea, hepatosplenomegaly, muscular weakness, osteoporosis, anemia, leukothrombocytopenia, hyperammonemia and orotic aciduria after a high-protein intake. Hyperdibasicamino-aciduria was associated with subnormal plasma concentrations of the same aminoacids. Oral l-arginine, l-ornithine, l-lysine, and lysyl-glycine loads confirmed the diagnosis. The supplementation of the diet with l-citrulline resulted in normal levels of blood ammonia. However, hepatosplenomegaly, muscular weakness, osteoporosis remained unchanged and growth was not improved. These may be due to lysine deficiency.

Amino Acid Metabolism, Inborn Errors↗
PubMed1982

[Neonatal hyperammonemia due to ornithine transcarbamylase deficiency (author's transl)].

The clinical and biochemical findings in a patient with the inherited disease so called hyperammonemia type II are presented. The patient was a male who had the first abnormal symptoms of tremors and continuous crying at 35 hours of age and exhibited a rapid clinical course dying 62 hours after birth. Rejection of food, respiratory problems, hypotonia and tonic-clonic convulsions were other outstanding clinical symptoms observed. Withdrawal of the feedings and initiation of a perfusion did not improve the clinical picture. Biochemical studies in samples of blood, urine and CSF revealed the presence of high concentrations of ammonia, alanine, glutamine and orotic acid. Final diagnosis was achieved when post mortem liver ornithine transcarbamylase activity was found to be lower than 6% with respect to that of adequate controls. Carbamyl phosphate synthetase, another urea cycle enzyme measured, was within normal limits of activity.

Amino Acid Metabolism, Inborn Errors↗
PubMed1981

Cerebral enzymatic activities during chronic hyperammonemia and treatment with S-adenosyl-L-methionine, adenosine and methionine in the rat.

The effect of the chronic intramuscular administration of some agents related to the S-adenosyl-L-methionine system on the hyperammonemia syndrome was evaluated. This experimental syndrome was induced in the rat by intraperitoneal administration of high doses of ammonium acetate (33, 100 and 300 mg/kg/day, 6 days a week for 80 days) followed by the assay of the activities of some cerebral enzymes involved in energy transduction. The enzymatic activities studied in the homogenate and in the mitochondrial fractions of brain tissue were: lactate dehydrogenase, citrate synthase, malate dehydrogenase, total NADH-cytochrome c reductase and cytochrome oxidase. All three doses of ammonium acetate induced significant modifications in the cerebral enzymatic activities. These doses reduced the activity of the total NADH-cytochrome c reductase both in the homogenate and in the mitochondrial fraction. On the other hand the activity of malate dehydrogenase was reduced limited to the two lower doses in the homogenate only. The simultaneous daily treatment (i.m.) with equimolar doses of substances involved in the S-adenosyl-L-methionine system (adenosine, methionine and S-adenosyl-L-methionine) did not cause any significant modification of the cerebral enzymatic activities associated with the administration of ammonium acetate at the three dose levels, thus confirming our previous results.

Adenosine↗
PubMed1980

Dysautonomia in an infant with secondary hyperammonemia due to propionyl coenzyme A carboxylase deficiency.

A male infant who had vomiting and coma in the absence of ketoacidosis was initially thought to have dysautonomia because of abnormal responses to methacholine and histamine, as well as abnormal urinary catecholamine excretion. Following an episode of hyperammonemia, a liver biopsy was performed which revealed a partial deficiency of carbamyl phosphate synthetase activity. The patient was treated with a protein-restricted diet supplemented with a mixture of ketoacid analogues of the essential amino acids, which precipitated ketosis and acidosis. A primary deficiency of propionyl coenzyme A (CoA) carboxylase was subsequently demonstrated. Because disorders of propionate metabolism may not initially present with ketoacidosis, we recommend examination of both plasma and urine for metabolites of this pathway, as well as direct measurement of propionyl CoA carboxylase activity in peripheral blood leukocytes, before performing a liver biopsy to evaluate urea cycle enzyme activities, and particularly before adding keto acid/amino acid mixtures to a protein-restricted diet.

Acyl Coenzyme A↗
PubMed1994

Changes in distribution and activity of glutamine synthetase in carbon tetrachloride-induced cirrhosis in the rat: potential role in hyperammonemia.

Cirrhosis induced in rats by carbon tetrachloride was used to study alterations in the activities and lobular distribution of carbamoylphosphate synthetase and glutamine synthetase. Specific activity of carbamoylphosphate synthetase in cirrhotic subjects was decreased to 70% of controls. Staining was homogeneous within micronodular areas, but varied from area to area and generally showed a decreased intensity. Specific activity of glutamine synthetase and the size of the glutamine synthetase-positive area were decreased to 20% and less of controls. Glutamine synthetase-positive hepatocytes were rare and scattered at the periphery of nodular areas and within fibrous septa, the normal association with the central veins being widely lost. Rarely, complete micronodules showed a slight homogeneous staining for glutamine synthetase. Arginase activity was not affected, whereas glutaminase activity was enhanced by 50%. Serum levels of ammonia were elevated more than 2-fold and those of glutamine by 30%. In contrast, urea levels tended to be slightly diminished. Serum ammonia levels showed a clear negative correlation with the specific activity of glutamine synthetase and the size of the glutamine synthetase-positive area. Furthermore, blood urea levels correlated with the sum of ammonia and glutamine concentrations, but not with each of these substrate concentrations alone. These data suggest that the changes in activity and distribution of glutamine synthetase contribute to hyperammonemia in cirrhosis. Despite a reduced activity of the initial enzyme of the urea cycle, urea synthesis is not diminished accordingly. This may be due to an enhanced flux caused by the elevated blood level of ammonia and an increased hydrolysis of glutamine, because of higher levels of glutaminase.

Ammonia↗
PubMed1996

Idiopathic hyperammonemia: a frequently lethal complication of bone marrow transplantation.

Idiopathic hyperammonemia (IHA) has been described as a rare complication of intensive chemotherapy, but there is little data regarding its occurrence after bone marrow transplantation (BMT). IHA is defined as elevated plasma ammonia concentrations (> 200 mumol/l) in the absence of significant liver function abnormality. From a 21 year BMT database of 2358 patients, we have identified 12 patients (0.5%) with IHA, ages 19 to 46 years. Diagnoses included ALL (n = 2), AML (n = 4), CLL (n = 1), CML (n = 3) and aplastic anemia (n = 2). Eight received marrow from a matched sibling donor, three from an unrelated donor and one autologous marrow. IHA occurred between 14 and 106 days after transplant (median, 25 days). Most frequently patients presented with symptoms of a metabolic encephalopathy, with lethargy and confusion evolving into unresponsiveness, metabolic coma and in eight cases, seizures. At diagnosis of IHA, liver functions were normal or only modestly abnormal. Ten of the 12 patients died 1 to 9 days (median 3.5 days) after diagnosis of IHA despite treatment with combinations of dialysis and ammonia-trapping therapy. While IHA is a rare complication of BMT, it is associated with a high mortality. Early recognition of the syndrome by measurement of plasma ammonia concentrations in patients with neurological symptoms may improve outcome.

Adult↗
PubMed1997

[Efficacy of various therapeutic measures in metabolic hyperammonemia].

OBJECTIVE: The aims of this work were to describe the therapeutic options available for severe hyperammonemia in children when ammonium levels are so high that the child's neurologic future or even their life is compromised. In addition, a comparison of the relative efficacy of each therapeutic method is made. PATIENTS AND METHODS: We present six cases, five of which suffered from inborn errors of metabolism and a six which presented with Reye's syndrome, all of whom presented or developed hyperammonemic coma. Their initial ammonium levels fluctuated between 300 and more than 2000 micrograms per deciliter. The treatment was made with exchange transfusion (ET), ET and peritoneal dialysis (DP) together or hemodialysis (HD). RESULTS: Peritoneal dialysis was the method that obtained the greatest reduction in plasma ammonium levels. However, the quickest reduction was observed with ET and HD. There were no significant complications with any of the methods except for hemodynamic deterioration in one patient during HD. CONCLUSIONS: We believe that HD is the treatment of choice for these patients because it is able to obtain a quick and lasting clearance of plasma ammonium. However, this method is not always available and has not been used very often in small babies. In these cases, the combined use of ET and DP can be very useful.

Ammonia↗
PubMed1997

The glial glutamate transporter in hyperammonemia and hepatic encephalopathy: relation to energy metabolism and glutamatergic neurotransmission.

Abnormalities in glutamate metabolism and glutamatergic neurotransmission appear to play a major role in the pathogenesis of hyperammonemia and hepatic encephalopathy. Astrocytes may be involved in these derangements as ammonia has been shown to impair the ability of these cells to take up glutamate. This study presents a northern blot analysis of the GLT-1 glutamate transporter in hyperammonemic rats, and in rats with thioacetamide-induced acute liver failure. Our findings demonstrate a downregulation of GLT-1 mRNA in both conditions. This article examines the potential impact of deficits in glutamate uptake on energy metabolism and glutamatergic neurotransmission in the context of abnormalities in glial-neuronal interactions. We propose that an ammonia-induced abnormality in astroglial glutamate uptake constitutes a critical aspect in the pathogenesis of hepatic encephalopathy and other hyperammonemic conditions.

ATP-Binding Cassette Transporters↗
PubMed1998

A case of severe hyperammonemia and unconsciousness following sodium valproate intoxication.

Although valproic acid has gradually gained its popularity in the treatment of various seizure disorders, overdose of valproate is not common. An 18-y-old man with a history of epilepsy controlled by sodium valproate and clonazepam attempted suicide with an ingestion of 45 g sodium valproate. He presented to our service with drowsiness and irritability. Extremely high serum ammonia (623 ug/dL) and elevated serum valproate concentration (575 ug/mL) were found on admission. Several metabolic abnormalities, including hypernatremia, hypocalcemia and metabolic acidosis, as well as, increased serum transaminase levels were also recorded. With supportive measures, he became clear 24 h later and was discharged 6 d after ingestion. Serial follow-up of his serum valproate and ammonia levels disclosed a close relationship between these 2 measurables. After acute overdose of valproic acid, patients usually present with mild and generally reversible depression of the central nervous system. However, impairment of liver function, hyperammonemia, fluid-electrolyte disturbances, coma, seizures, hypotension and even death may occur following valproate overdose. Symptomatic and supportive measures are the mainstay in the treatment of valproic acid overdose. With prompt diagnosis and early institution of treatment, a complete recovery should be anticipated.

Adolescent↗